Improvement in dash-pots



e. H. CORLISS.

DASH-POT.

Patented June 6, 1876.

Fig/3.

Wiinessee engine is employed.

UNITED STATES Parana @rrroa GEORGE E. GOBLISS, OF PROVIDENCE, RHODEISLAND.

IMPROVEMENT IN DASH-POTS.

Specification forming part of Letters Patent No. 178,275, dated June 6,1876; application filed i October 27, 1875.

To all whom it may concern:

Be it known that I, GEORGE E. OoRLIss, of Providence, in the State ofRhode Island, have invented certain Improvements in Valve- ShuttingDevice for Steam-Engines, of which the following is a specification:

In all those classes of steam-engines in which the steam-valve isliberated and caused to close by means independent of the power by whichit is opened, it is important to provide means for moving the valverapidly, so that the steam shall be cut off with very littlewire-drawing. It is also important to gradually arrest the motion at itsclose, so as to avoid shock. My invention is for these purposes.

Springs of ordinary character are liable to change their tension withchanges of temperature and with lapse of time. They also act withvarying degrees of force, as they are more or less strained. It isimportant that the force of the closing-means applied to the valve shallbe practically constant, analogous to the force of gravity acting on aheavy weight. A weight is objectionable for the reason, among others,that its inertia forbids its starting rapidly from a state of rest, andmakes it diffieult to arrest its motion gently, when the valve has beenclosed.

It has been found that a piston actuated by the pressure of theatmosphere forms a desirable means for securing these conditions. Somehave tried to maintain a vacuum below such piston by keeping open acommunication therefrom to thecondenser, when a condensing- One of theobjections to this is the absence of a vacuum under some conditions,especially in the act of starting. Another lies in the variations of thevacuum at other periods.

I have constructed an improved apparatus making its own vacuum, alwaysfreely lubricated, and maintaining its vacuum with practical uniformityunder all conditions, and maintaining it throughout the entire closingmotion. The motion is arrested after the valve is closed by anair-cushion,sufficient to sion of the hissing noise ordinarily producedby the escape of air under pressure.

The accompanying drawings represent what I consider the best means ofcarrying out the invention.

Figure l is a central vertical section of the entire apparatus forclosing the steam-valve. In this figure the piston is in its lowestposition, corresponding to that which it maintains when the valve isshut, and all the parts are at rest. Fig. 2 is a cross-section throughsome of the parts in the plane, at right angles to the section inFig. 1. Fig. 3 is a corresponding plan view, and Fig. 4 is a sectioncorresponding to Fig. 2, but with all the parts. In Fig. 4L the pistonis being raised.

Similar letters of reference indicate like parts in all the figures.

A is a hollow cylinder, and A a corresponding'cylinder of largerdiameter formed in the same casting therewith. B is a foundationchamberfirmly supporting the duplex cylinder A A The bottom of the cylinder Ais tightly closed by a plate, as represented, with the exception of asmall central orifice, a. This orifice is closed by a tight-fittingvalve of leather, or other suitable material. marked 0, which is held upto the lower side of the orifice a by means of a spring, 0. The cylinderbottom and the spring 0 are both firmly held up in their places byshoulders or webs formed in the interior of the chamber B, as indicatedin Figs. 1 and 3. It follows that the bottom of the cylinder A is ableto discharge through the valve-orifice a any oil or other contents whensufficiently forced to overcome the spring. The piston which is raisedand dropped in the cylinder A A I will designate, when required, by thesingle letter I). Its two diameters correspond to the diameters of thecylinders A A The small part of the piston I will designate as and thelarger as D The small part, B, is tightly packed by a cup-leather, d. Ascrew-thread on the stem or shank d of the lower piece (1 allows thiscup-leather d to be held firmly. In the annular portion of the casting DD are a series of air-holes, m, covered on the under side by valves m ofleatheror other flexible material. E is a passage cored through thecasting A A and communicating with an orifice in the top of the castingB. The effect ive area of this passage is controlled by the screw 0. Itspoint of communication with the interior of the cylinder A isconsiderably above the bottom of said cylinder. G is a link or rod, theupper end of which takes hold of the valve mechanism, (not represented,)so that, by pulling down on the rod G, the steamvalve (not shown) isclosed. The lower end of this rod Gr takes hold of the compound piston Dthrough the pin H and center-casting I. When the steam-valve is opened,the opening action lifts on the rod G and raises the piston B into theposition shown in Fig. 4. During this motion the valves m open downwardand fill the annular space below the large part D with air, while thespace below the small piston D is a vacuum. The moment the valve isliberated the piston descends rapidly by virtue of the vacuum under thesmall piston D but when the piston has descended nearly to its lowestposition. the air in the annular space under the large piston D whichhas been escaping through the passage Eis cut off by the descent of thelarge part I) below the port or upper ends of the passage E. The airbelow the large piston D now serves as a cushion, and rapidly but gentlyarrests the motion.

In cases in which the oil has entered the vacuum under the small pistonD it will be driven out through the orifice a by a slight opening of thevalve 0 at each descent of the piston. Oil is to be added at properintervals, or constantly at the top, and allowed to work \down, keeping,all the rubbing surfaces well lubricated. The central casting I servesas a nut to connect with a thread at the upper end of the stem or shank(1 below. The lower portion of the casting I applies within the smallportion D of the piston, while its upper end is larger, and rests on theshoulder or offset between the large and small parts. The pin H, whichengages with the valve-rod G, is correspondingly formed andcorrespondingly supported bythe offset in the piston. It is thus firmlyheld against any movement, either endwise or rotatory,and all the partsmay be readily separated for cleaning or repairs. If desired,

two or more rods may, in any instance, en-

gage with the same pin, H. So, also, other means than the screw 6 may beused for controlling the area of the passage E, or the device may worksuccessfully with the passage E always freely open so long as its upperend or port is sufficiently above the oli'set which forms the bottom ofthe large cylinder A The air which is forced down the passage E at eachclosing of the valve may be allowed to escape through a passagespecially provided, or through the joints between the castings B A A Iesteem it important, however, that it shall not be discharged from thepassageE directly into the atmosphere, but into an inclosed space, likethe oil-chamber B, from whence it may emerge gently and withoutobjectionable noise.

I claim as my invention- 1. In combination with a connection, G, leadingto the steam-valve ot' a steam-engine, the valve-shutting devicedescribed, having a pis ton working in a cylinder, and a self-actingvalve openingoutward therefrom, the whole -adapted to form a vacuum eachtime the piston is raised, substantially as herein specified.

2. The compound or duplex piston I) D and connection G therefrom, incombination with the cylinders A A so arranged that one part of thepiston is equipped to serve with a vacuum to induce motion, and theother part to cushion the air to arrest motion, as hereinspecified.

3. In combination with a large or cushioning piston, D and theconnection G, leading therefrom, as shown, the air-passage E, leadingfrom the large cylinder D to a capacious chamber, B, and. adapted tosoften and reduce the soundof the escaping air, as herein specified.

4. The central casting I and pin H, formed with an oii'set, as shown, incombination with the threaded stem 01, and with a piston having anofi'set in its interior adapted to engage therewith, as and for thepurposes herein specified.

In testimony whereof I have hereunto set my hand this 6th day ofOctober, 1875, in the presence of two subscribing witnesses.

. GEO. H. (JORLISS.

Witnesses:

GEORGE G. PHILLrPs, ED. W. RAYNsFoRD.

